Semiconductor device packages are comprised of different types of active devices incorporated within the package that serve various functions. Semiconductor packages include CMOS (complementary metal oxide semiconductor) devices such as chips built on a silicon substrate or wafer. In some instances, the CMOS chip may be an application-specific integrated circuit (ASIC) chip which is generally classified as a chip having an integrated circuit (IC) that is custom built for a specific end use or purpose. Some ASIC chips may be a system-on-chip (SoC) which includes a processor, memory devices, and other ancillary components that are built on an application specific chip.
MEMS devices of various types are sometime incorporated into the semiconductor package to augment and support the functionality of the ASIC chips in the package. MEMS devices are micro-sized devices or machines that may have stationary and/or movable elements that provide some type of electro-mechanical functionality desired for a particular application and system. Some type MEMS devices which may be found in a semiconductor chip package may include, for example without limitation, micro-timing devices (i.e. resonators, oscillators, real-time clocks, clock generators, etc.), micro-sensors (e.g. pressure and temperature transducers that convert mechanical movement or displacement into electrical signals), micro-actuators, accelerometers, micro-switches, micro-pumps and valves, and others that support and assist with controlling the functionality of the chip(s) in the package and/or system-level integrated circuit (IC).
MEMS devices have dimensions that may fall in a range from less than 1 micron to several millimeters in size. MEMS devices may be constructed on a silicon substrate or wafer similarly to CMOS chips by using various fabrication techniques including without limitation bulk micromachining of the silicon substrate itself and/or surface micromachining involving building microstructures on the surface of the substrate using various semiconductor IC fabrication technologies such as material deposition, patterned photolithography, and etching. The foregoing manufacturing techniques may be used to construct many different types of MEMS devices from simple structures with no moving elements to complex electromechanical systems having a plurality of moving elements that may be controlled by integrated microelectronics. The MEMS chip is mounted in the semiconductor package at the wafer level with the ASIC chip.
MEMS devices and their performance are sensitive to operating temperature and temperature fluctuations which may be caused by swings in ambient temperatures and cause differential thermal expansion problems of the elements used to construct the MEMS device since different types of materials used may each have different coefficients of thermal expansion. Thermal excursions due to ambient temperature excursions may also cause temperature induced voltage drift and other similar electrical problems adversely affecting the performance of the MEMS. Accordingly, it is desirable to regulate and control the operating temperature of the MEMS device independent of the ambient operating environment temperature in which the device may be located. Optimally, it is beneficial that the operating temperature of the MEMS device remain relatively uniform or stable during its operation irrespective of changing ambient conditions or operating environments to avoid operating temperature swings and potential performance problems.
An improved temperature control system for MEMS devices is desired.
All drawings are schematic and are not drawn to scale.